Avalon ST custom IP component

Thank you for your answer. Actually I didn't have to perform any simulation as my mistake was in the ready latency, but I fixed it and now I'm able to send data through my component.

Now I have another problem because I need to modify the data that comes through my IP but I'm not quite sure how to interpret the fact that the data is sent with the control packet. My first thought was that if I have a 24 bit wide data stream the 3 x 8 bits correspond to the R,G,B values respectively and that's it. But when I tried to change the data the component stops working. The Avalon specification doesn't state if I should take something into consideration when accessing the data.

Do you have any experience in that?